'Morden' probably means the hill in the marshland.
It is thought to come from Old English mōr, marsh, and dūn, hill, for its slightly raised ground between the Beverley Brook and the River Wandle; other suggested meanings are ‘great fort’ and ‘town on the moor’. A will of 1015 mentions ‘land at Mordune’, and the Domesday Book of 1086 records Mordone. Morden is the end of the Northern line and the southernmost station on the Underground.